1. Field of the Invention
The present disclosure relates to a voice coil motor.
2. Discussion of the Related Art
In general, a small optical device such as a camera on a mobile phone or a digital camera is formed with an actuator for adjusting magnification and focus. The camera on the mobile phone or the digital camera recently employs an actuator such as a VCM (voice coil motor) on a wide range base.
The VCM is a motor that uses a vibration plate of a speaker by utilizing the magnetic field generated by a current flowing in a voice coil of a speaker and a magnetic field generated by a permanent magnet. The VCM is advantageous in that it consumes less electric power, is less voluminous and inexpensive and has a high accuracy in operation displacement, such that the VCM is adequate in adjusting a gap between a lens and an image sensor in a camera module.
The VCM includes a base, a rotor, a stator, a yoke and a housing. The rotor is arranged on the base, the rotor lifts up and down relative to the stator, the yoke covers the rotor and the stator and the housing is directly connected to the base to cover the rotor, the stator and the yoke. In a case a housing made of synthetic resin is used in the conventional VCM, the housing in the camera module cannot block the electromagnetic wave generated from various elements in a confined space and area. Furthermore, the voluminous housing can hardly increase size of a permanent magnet and a coil formed inside the yoke to produce a weak driving power. Still furthermore, the VCM is susceptible to impact and/or vibration due to the housing fixing the yoke being made of synthetic resin.